In-forest log segregation based on acoustic measurement of wood stiffness

Abstract:

To remain competitive, the forest products industry needs to look for new and
innovative processes and technologies to not only reduce costs but also to recover
more value through the entire seedling-to-customer forest products supply chain. It
is well recognized that measuring wood properties of logs in real time during
harvesting would lead to improved log allocation decisions and increased value
recovery. Wood stiffness is certainly one of the attributes defining the quality of
forest products such as veneer and lumber. Accurately assessing stiffness in realtime
can be a challenge for log supply managers requiring logs segregated into
different product classes based on stiffness.
Acoustic technology has proven to be a well established non-destructive technique
for assessing potential product performance by identifying logs with high stiffness.
Launched by the worldwide trend towards increased mechanization of forest
harvesting operations, providing a platform for innovative measurement systems,
the interest in incorporating technologies for measuring internal stem features into a
harvester head is rapidly growing. Therefore, the purpose of this study was to
provide forest products stakeholders with comprehensive scientific information on
the potential capabilities, limitations, and applicability of acoustic technology to
improve value recovery from Douglas-fir stands by means of in-forest sorting of
veneer quality logs.
This dissertation:
• Demonstrated that recovery of high quality green veneer from Douglas-fir
peeler logs could be accurately predicted using resonance-based acoustic
velocity measurements,
• modeled the predictive capabilities of spatial as well as internal and external
log and tree characteristics in terms of veneer quality and analyzed their
effects on acoustic velocity measurements of Douglas-fir wood stiffness,
• determined whether time of flight acoustic technology could be used for
pre-harvest veneer quality assessment of Douglas-fir stands in terms of
stiffness requirements,
• described influential factors arising from incorporating acoustic instruments
on a mechanized harvester head and suggested optimal procedures for
scanning in terms of feasibility and harvester productivity,
• presented a general methodology to estimate breakeven prices of Douglasfir
peeler logs based on the net return obtained when logs from stiffness
graded stands using acoustic technology are processed and converted into
end products.